Patent GB-786922-A (GB)
Title: Improvements in or relating to gas-mixture fractionating apparatus
IPC: F25J3/04
Filed: 1955-10-26
Abstract: 786,922. Cold separation of air. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Oct. 26, 1955 [March 30, 1955], No. 30627/55. Class 8(2). In a binary gasmixture, e.g., air fractionating apparatus comprising a column 1, Fig. 1, or boiler 2 to which crude liquid oxygen from the column 1 passes down a conduit 4, a thermal sink, e.g., a gas refrigerator 14 of the reversed hot gas engine type adapted to condensenitrogenwithdrawn from the column head through a duct 12 and supply it through ducts 13, 16, 18 as reflux and through ducts 19, 20, as product, the column 1 is also connected to the boiler 2 by two vapour-supplying ducts 22, 23, one 23 of which is adapted to be closed at a predetermined level of liquid in the boiler and is provided with heat conducting means, e.g., a metal strip 32, Fig. 2, serving to control the flow of reflux nitrogen up the duct 18. The duct 23 extends below duct 22 and has its lower end 31 cut obliquely to effect closure by a rise in level of the liquid oxygen in the boiler 2. Down portions 24, 25 of the ducts 22, 23 lead to a duct 26 having a valve-controlled port 27 opening into the column 1 and are connected by metal strips 33, 32 to liquid nitrogen tubes 19, 18 rising from a manifold 17 which is supplied from the duct 16. The said down portions also have extensions 29, 30 dipping below the liquid level in the boiler 2. In operation air is drawn by the sub-atmospheric pressure in the condensation chamber of the refrigerator 14 through a duct 10 past water and carbon-dioxide condensing fins 7 and through a duct 11 to the column 1, and reflux liquid nitrogen is forced up the duct 18 by a bubblepump action, the heat energy for which is derived by conduction along the strip 32. Thus in the event of a fall in the level of liquid in the boiler 2 below the duct end 31, the relatively warm crude oxygen vapour of varying composition and temperature ascending duct 23 warms the strip 32 and hence the bottom end of duct 18, thereby increasing the pumping action to provide more reflux which in turn restores the liquid level in the boiler 2. Discharge of product liquid nitrogen by bubble pump action up duct 19 and past a liquid lock 21 is similarly controlled by the strip 33. In a modification reflux nitrogen traverses apertures 46, Fig. 6, at the base of a storage chamber 45 supplied from the refrigerator 14 through a duct 49 in accordance with the level of a pivoted overflow duct 48 controlled by a bellows 51 which in turn is controlled by a gas thermometer tube 66 opening thereto and having its lower end open to a vessel 60 partly filled with liquid nitrogen and connected by the strip 32 to the vapour duct 23. Thus when the lower end 31 of the duct 23 is above the level of liquid in the boiler 2 the temperature and hence the pressure of the gas thermometer rises, the bellows 51 extend, the overflow duct 48 rises and so allows a higher head of reflux in the chamber resulting in a greater flow through the apertures 46 which in turn restores the level in the boiler 2. Specifications 668,621 [Group XIII] and 746,436 are referred to.